The Third Generation Partnership Project (3GPP) proposes a long term evolution/system architecture evolution (LTE/SAE) network. The purpose of the LTE network is to reduce delay, to increase user data rate, to improve system capacity, and to lower coverage costs. For better description, the SAE network architecture is divided into the following two parts, as shown in FIG. 1.
The first part includes a user equipment (UE) 101, a radio access network (RAN) 102, a serving general packet radio service support node (SGSN) 103, and a packet data network gateway (PGW) 104.
The RAN consists of a radio network controller (RNC) and a NodeB. The RNC is adapted to allocate and control radio resources of the NodeB connected to or related to the RNC. The RNC implements functions such as connection setup and disconnection, handover, macro diversity combining (MDC), and radio resource management control. The NodeB converts data streams and manages a part of radio resources.
The SGSN is responsible for forwarding input/output Internet Protocol (IP) packets for UEs in a local service area. The SGSN provides functions such as routing and forwarding of packets in the local service area, provision of services for all the UEs in the local service area, encryption and authentication, session management, and mobility management. The SGSN 103 is an SGSN of 3GPP R7 or earlier versions. The SGSN 103 is designed to enable the SAE architecture to be compatible with earlier systems.
The PGW is responsible for connecting a UE to a user plane anchor point of a packet data network (PDN) and communicating with external PDNs. It is also responsible for routing and forwarding packets, enhancing policy charging, filtering packets based on each user. In addition, the PGW is connected to an operator's IP network.
The second part includes a UE 101, an RAN 105, an SGSN 106, a serving gateway (SGW) 107, and a PGW 104.
The SGW stores user plane contexts of the UE, for example, IP address and routing information of the UE, and performs lawful interception and packet data routing.
The SGSN 106 is an SGSN of 3GPP R8, and can communicate with the SGW directly.
A method for setting up a bearer in the prior art is based on an SGSN of 3GPP R7 or earlier versions, which can be connected to the PGW directly. Thus, a bearer between the UE and the PGW can set up through the RAN and the SGSN.